Sulfur Transformations in Forest Litter and Soil: Results of Laboratory and Field Incubations
1988
Watwood, M. E. | Fitzgerald, J. W.
Field incubations of litter (01 and 02 layers) and A horizon soil utilizing ³⁵S-labeled inorganic sulfate were conducted during July 1985 in an eastern white pine (Pinus strobus L.) and a hardwood forest. Samples were assayed for the capacity to form ³⁵S-labeled organic S, and in most cases these capacities were very similar to those determined in corresponding laboratory incubations. The A horizon soils from both watersheds formed approximately 3.0 nmol of organic S g⁻¹ dry weight of sample during 2-d field or laboratory incubations. No substantial increase in this amount was observed after 7-d field incubations. Intrinsic S fractions of samples were quantified prior to and following field incubations, and organic S represented the majority of the total S in all cases. Total S ranged from 260 to 1180 and from 150 to 270 mg kg⁻¹ in the litter layers and the A horizon, respectively. Sulfonate S (13–74% of total S) and nonphosphate extractable ester sulfate (16–82% of total S) were the largest organic S pools. Water soluble and phosphate extractable S pools were comprised of both inorganic sulfate and ester sulfate, and the latter was found to represent up to 8.1% of total S. The distribution of ³⁵S following field incubations was determined, and organic ³⁵S fractions in a variety of linkage groups were again found to predominate. Total C, moisture content, and throughfall sulfate concentrations during the field incubations were also determined. Research conducted as part of the Integrated Forest Study.
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